// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use ast;
use parse::new_parse_sess;
use parse::{ParseSess,string_to_filemap,filemap_to_tts};
use parse::new_parser_from_source_str;
use parse::parser::Parser;
use parse::token;
use ptr::P;
use str::char_at;

/// Map a string to tts, using a made-up filename:
pub fn string_to_tts(source_str: String) -> Vec<ast::TokenTree> {
    let ps = new_parse_sess();
    filemap_to_tts(&ps,
                   string_to_filemap(&ps, source_str, "bogofile".to_string()))
}

/// Map string to parser (via tts)
pub fn string_to_parser<'a>(ps: &'a ParseSess, source_str: String) -> Parser<'a> {
    new_parser_from_source_str(ps,
                               Vec::new(),
                               "bogofile".to_string(),
                               source_str)
}

fn with_error_checking_parse<T, F>(s: String, f: F) -> T where
    F: FnOnce(&mut Parser) -> T,
{
    let ps = new_parse_sess();
    let mut p = string_to_parser(&ps, s);
    let x = f(&mut p);
    p.abort_if_errors();
    x
}

/// Parse a string, return a crate.
pub fn string_to_crate (source_str : String) -> ast::Crate {
    with_error_checking_parse(source_str, |p| {
        panictry!(p.parse_crate_mod())
    })
}

/// Parse a string, return an expr
pub fn string_to_expr (source_str : String) -> P<ast::Expr> {
    with_error_checking_parse(source_str, |p| {
        p.parse_expr()
    })
}

/// Parse a string, return an item
pub fn string_to_item (source_str : String) -> Option<P<ast::Item>> {
    with_error_checking_parse(source_str, |p| {
        p.parse_item()
    })
}

/// Parse a string, return a stmt
pub fn string_to_stmt(source_str : String) -> P<ast::Stmt> {
    with_error_checking_parse(source_str, |p| {
        p.parse_stmt().unwrap()
    })
}

/// Parse a string, return a pat. Uses "irrefutable"... which doesn't
/// (currently) affect parsing.
pub fn string_to_pat(source_str: String) -> P<ast::Pat> {
    string_to_parser(&new_parse_sess(), source_str).parse_pat()
}

/// Convert a vector of strings to a vector of ast::Ident's
pub fn strs_to_idents(ids: Vec<&str> ) -> Vec<ast::Ident> {
    ids.iter().map(|u| token::str_to_ident(*u)).collect()
}

/// Does the given string match the pattern? whitespace in the first string
/// may be deleted or replaced with other whitespace to match the pattern.
/// this function is Unicode-ignorant; fortunately, the careful design of
/// UTF-8 mitigates this ignorance.  In particular, this function only collapses
/// sequences of \n, \r, ' ', and \t, but it should otherwise tolerate Unicode
/// chars. Unsurprisingly, it doesn't do NKF-normalization(?).
pub fn matches_codepattern(a : &str, b : &str) -> bool {
    let mut idx_a = 0;
    let mut idx_b = 0;
    loop {
        if idx_a == a.len() && idx_b == b.len() {
            return true;
        }
        else if idx_a == a.len() {return false;}
        else if idx_b == b.len() {
            // maybe the stuff left in a is all ws?
            if is_whitespace(char_at(a, idx_a)) {
                return scan_for_non_ws_or_end(a,idx_a) == a.len();
            } else {
                return false;
            }
        }
        // ws in both given and pattern:
        else if is_whitespace(char_at(a, idx_a))
           && is_whitespace(char_at(b, idx_b)) {
            idx_a = scan_for_non_ws_or_end(a,idx_a);
            idx_b = scan_for_non_ws_or_end(b,idx_b);
        }
        // ws in given only:
        else if is_whitespace(char_at(a, idx_a)) {
            idx_a = scan_for_non_ws_or_end(a,idx_a);
        }
        // *don't* silently eat ws in expected only.
        else if char_at(a, idx_a) == char_at(b, idx_b) {
            idx_a += 1;
            idx_b += 1;
        }
        else {
            return false;
        }
    }
}

/// Given a string and an index, return the first usize >= idx
/// that is a non-ws-char or is outside of the legal range of
/// the string.
fn scan_for_non_ws_or_end(a : &str, idx: usize) -> usize {
    let mut i = idx;
    let len = a.len();
    while (i < len) && (is_whitespace(char_at(a, i))) {
        i += 1;
    }
    i
}

/// Copied from lexer.
pub fn is_whitespace(c: char) -> bool {
    return c == ' ' || c == '\t' || c == '\r' || c == '\n';
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test] fn eqmodws() {
        assert_eq!(matches_codepattern("",""),true);
        assert_eq!(matches_codepattern("","a"),false);
        assert_eq!(matches_codepattern("a",""),false);
        assert_eq!(matches_codepattern("a","a"),true);
        assert_eq!(matches_codepattern("a b","a   \n\t\r  b"),true);
        assert_eq!(matches_codepattern("a b ","a   \n\t\r  b"),true);
        assert_eq!(matches_codepattern("a b","a   \n\t\r  b "),false);
        assert_eq!(matches_codepattern("a   b","a b"),true);
        assert_eq!(matches_codepattern("ab","a b"),false);
        assert_eq!(matches_codepattern("a   b","ab"),true);
    }
}